Bidirectional fibre=optic link for cable TV - has large dia. step refractive index fibres and gradient index fibre for carrier transmission

摘要

The cable provides a link between two stations (A,B). The energy transmitter-receivers of each station are optically coupled to a single link cable (Ca) which comprises an optic fibre of step index (f2) (large dia. fibres) and an optic fibre of gradient index (f1), the latter being made e.g. by modified vapour chemical deposition. The cable has an axial fibre of step index forming the carrier element and one or more gradient index fibres colinear with the axial fibre. Alternatively the axial fibre is of step index while the gradient index fibre is coiled about the axial fibre. A plastics protective coating (1) is provided together with aromatic polyamide fibres embedded in the plastics parallel with the step index fibre.